handling ejb3 injection failure

[ajay662]

In my servlet I want to inject an EJB, only if its available.

@EJB
MyBeanClass myBean;

My requirement is that 'myBean' gets initialized if corresponding EJB is available in the application, otherwise it stays NULL.

Is there a way to achieve this? Is there a way to catch injection exceptions?

I don't want to do a lookup since lookup requires knowledge of application name as well and I don't want to depend on that.

[alrubinger]

The @EJB Annotation does more than injection; it also establishes a dependency.

For a JBoss-specific solution, you can also annotate your instance variable with @IgnoreDependency like:

@EJB
@IgnoreDependency
MyBeanClass myBean;

...which I believe should work, though I've never tried this use case specifically. One thing it won't do is inject "myBean" if "MyBeanClass" is deployed *after* your other service - the container won't keep track of what injections it should perform if they're deployed at a later time.

Also, your lookups don't necessarily have to point to a JNDI address that includes the application name. JBoss assigns these by default, but you can override with ejb-jar.xml or the @RemoteBinding/@LocalBinding annotations.

S,
ALR

[ajay662]

Thanks for your suggestions ALR.

I have tried @IgnoreDependency in my other jboss-specific app and it does work fine.

In this case however, I am actually looking for a portable solution and not something thats specific to a vendor.

[alrubinger]

In that case, would recommend using traditional Context.lookup() calls to get at your services, and would additionally bind each service to the container-non-specific local ENC in JNDI using container-specific metadata. This is actually discussed in another thread today:
http://www.jboss.org/index.html?module=bb&op=viewtopic&t=117939

S,
ALR

[bensonfungjava]

Hi,

I tried @IgnoreDepency, but it doesn't work for some reasons.
The following are my code of servlet, please help

package com.myejb3.servlet;

import javax.ejb.EJB;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.servlet.http.HttpServlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.jboss.annotation.IgnoreDependency;

import com.myejb3.intf.MyEJB3_1;

/**
* Servlet Class
*
* @web.servlet name="MyEJB3_1"
* display-name="Name for MyEJB3_1"
* description="Description for MyEJB3_1"
* @web.servlet-mapping url-pattern="/MyEJB3_1"
* @web.servlet-init-param name="A parameter"
* value="A value"
*/
public class MyEJB3_1Servlet extends HttpServlet {


@EJB
@IgnoreDependency
MyEJB3_1 myejb3;
public MyEJB3_1Servlet() {
// TODO Auto-generated constructor stub
}



protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException,
IOException {
// TODO Auto-generated method stub
super.doGet(req, resp);
this.doPost(req, resp);
}

protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException,
IOException {
// TODO Auto-generated method stub
String userName = (String)req.getParameter("username");
String password = (String)req.getParameter("password");
/* try {
InitialContext ctx = new InitialContext();
MyEJB3_1 myejb3 = (MyEJB3_1) ctx.lookup("demo_ejb/MyEJB3_1Bean/local");
myejb3.setName(userName);
myejb3.setPassword(password);
} catch(NamingException e) {
e.printStackTrace();
}*/

myejb3.setName(userName);
myejb3.setPassword(password);

getServletConfig().getServletContext().getRequestDispatcher("/result.jsp").forward(req, resp);
}

}


Thanks
Benson

[bensonfungjava]

Hi,

My JBOSS version is 4.2.1

Thanks
Benson

[alrubinger]

Injection for Servlets isn't supported until the 5 Series, currently in its second Beta release..

http://www.jboss.com/index.html?module=bb&op=viewtopic&t=107353

S,
ALR